U.S. patent number 7,209,600 [Application Number 10/178,872] was granted by the patent office on 2007-04-24 for synchronization of components for printing.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Stephen F. Goldberg.
United States Patent |
7,209,600 |
Goldberg |
April 24, 2007 |
Synchronization of components for printing
Abstract
The present invention relates to a technique for detecting that
all components that make up a completed portion of a form are
synchronized. A method is provided for detecting that for a print
job, all of the components that make up a completed portion of each
form are printed in synchronicity or in the case of an error in
synchronicity, an error condition is asserted. The print job
comprises at least one form, and each form may contain more than
one image, each image may contains one or more image planes and the
images on each form of a document may vary. Each image contains a
composite image group (CIG) mark comprising the set of image plane
coordination (IPC) marks associated with each individual image
plane. An IPC mark is printed by each print engine such that it is
possible via inspection of these marks to determine if the complete
set of image planes that make up a specific image are present. The
present invention allows one to confirm, using the CIG marks, that
all forms in a print job are synchronized.
Inventors: |
Goldberg; Stephen F. (Dayton,
OH) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
29717891 |
Appl.
No.: |
10/178,872 |
Filed: |
June 24, 2002 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20030234959 A1 |
Dec 25, 2003 |
|
Current U.S.
Class: |
382/294; 382/112;
382/151 |
Current CPC
Class: |
G06K
15/00 (20130101); G06K 2215/0091 (20130101) |
Current International
Class: |
G06K
9/32 (20060101); G06K 9/00 (20060101); G06K
9/36 (20060101) |
Field of
Search: |
;382/103,112,141,151,287,294 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wu; Jingge
Assistant Examiner: Tucker; Wes
Claims
What is claimed is:
1. A method for detecting synchronization of all image planes that
make up a completed form for a print job on a printer, the printer
capable of printing on a print media with an associated print
engines, the print job including a plurality of forms, each form
having a form origin and each form containing a plurality of image
planes, where the image planes that constitute an image are
referred to as a composite image, and wherein each composite image
can vary from form to form, the method comprising the steps of:
applying at least one image plane coordination mark to each of the
plurality of image planes that comprise the composite image on each
form, the at least one image plane coordination mark for each image
plane resulting in a plurality of image coordination marks, each of
the plurality of image coordination marks being located at defined
positions relative to the image plane coordination marks for the
other image planes of the corresponding image in the composite
image; forming a composite image group mark with the plurality of
image coordination marks, the composite image group mark including
an origin defined as a leading edge of a first of the plurality of
image plane coordination marks being offset a known distance,
definable as an offset distance, from the form origin; changing the
offset distance from the form origin for each composite image group
mark associated with subsequent forms such that an image plane
synchronization error will cause relative placement of at least one
of the plurality of image plane coordination marks to deviate from
its defined placement relative to any other of the plurality of
image plane coordination marks; detecting that the plurality of
image coordination marks of the composite image group mark of at
least one form are in a proper spatial relationship relative to
each other by detecting the absence of an image plane coordination
mark from the composite image group mark on the at least one form
or by detecting the presence of an image plane coordination mark
from the composite image group mark from another form on the at
least one form; and identifying proper synchronization if all of
the plurality of image coordination marks associated with the form
are in a proper spatial relationship to each other, or identifying
a synchronization error if at least one of the plurality of image
coordination marks associated with the form is not in proper
spatial relationship with the other image coordination marks
associated with the form.
2. A method as claimed in claim 1 wherein the offset distance
employed from one form to the next is a defined, repeated
pattern.
3. A method as claimed in claim 2 wherein magnitude of an image
plane synchronization error can be identified by a deviation in the
relative placements of the plurality of image coordination
marks.
4. A method as claimed in claim 1 wherein the offset distance
employed from one form to the next is changed by a random
amount.
5. A method as claimed in claim 1 wherein the at least one image
plane coordination mark comprises at least one images plane
coordination mark associated with each form of a print job.
6. A method as claimed in claim 1 wherein the step of detecting the
placement of the image plane coordination marks relative to each
other comprises the step of providing at least one electronic
sensor for detection the image plane coordination marks.
7. A method as claimed in claim 1 wherein the step of detecting
comprises the step of placing a plurality of electronic sensors in
a same spatial relationship to each other as the image coordination
marks are to each other, such that concurrent detection of the
image coordination marks by each of the plurality of electronic
sensors indicates a proper spatial relationship between the image
coordination marks.
8. A method as claimed in claim 1 wherein the step of detecting the
placement of the image plane coordination marks relative to each
other comprises the step of using human observation input.
9. A method as claimed in claim 1 wherein the step of detecting the
placement of the image plane coordination marks relative to each
other comprises the step of applying strobed illumination of each
form with its associated at least one image coordination mark.
10. A method as claimed in claim 1 wherein the step of detecting
the placement of the image plane coordination marks relative to
each other further comprises the step of marking documents that are
identified as not in synchronization.
11. A method as claimed in claim 1 wherein the step of detecting
the placement of the image plane coordination marks relative to
each other further comprises the step of forcing a shift in an
image plane identified as out of synchronization to put said image
plane in synchronization.
12. A method as claimed in claim 1 wherein the plurality of image
plane coordination marks are contiguously placed when each of the
plurality of image planes are in proper registration, and are not
contiguous when any of the plurality of image planes are
misregistered.
13. A method as claimed in claim 1 wherein the image plane
coordination marks are shifted parallel to direction of motion of
the print media past the printhead.
14. A method as claimed in claim 1 wherein the image plane
coordination marks are shifted parallel to direction of motion of
the print media past the printhead, and the image plane
coordination marks are placed between two forms.
15. A method as claimed in claim 1 wherein the image plane
coordination marks are shifted perpendicular to direction of motion
of the print media past the printhead.
16. A method as claimed in claim 1 further comprising the step of
printing a form distinguishing bar code on at least one image
plane, to identify defective forms for reprinting or to confirm
proper synchronization of all image planes of each document.
17. A method as claimed in claim 1 wherein synchronization errors
can be detected when the image plane coordination marks are only
printed on alternately printed forms.
18. A method for detecting errors in the synchronization of image
planes that make up forms in a print job, the method comprising the
steps of: associating an image plane coordination mark with each of
the image planes that make up a form; forming a composite image
group mark for each form, the composite image group mark including
a plurality of the image plane coordination marks that do not
overlap, each of the plurality of image plane coordination marks of
the composite image group mark including a readily detectable
relationship with the other of the plurality of image plane
coordination marks of the composite image group mark;
differentiating the composite image group mark of one form from the
composite image group mark of at least one other form such that the
readily detectable relationship between individual of the plurality
of image plane coordination marks that make up each composite image
group mark is intact if the image planes are properly synchronized
and the readily detectable relationship between individual of the
plurality of image plane coordination marks is broken if the image
planes are not properly synchronized; detecting whether the readily
detectable relationship between the plurality of image plane
coordination marks is intact or broken by detecting the absence of
an image plane coordination mark from the composite image group
mark of one of the forms or by detecting the presence of an image
plane coordination mark from the composite image group mark of one
of the forms on another form; and providing a synchronization
indication of whether the readily detectable relationship is intact
or broken.
19. A method as claimed in claim 18 wherein the readily detectable
relationship between the plurality of image plane coordination
marks comprises a defined spatial relationship between the
plurality of image plane coordination marks.
20. A method as claimed in claim 18 wherein the step of
differentiating the composite image group mark of one form from the
composite image group mark of at least one other form further
comprises the step of varying placement of the composite image
group mark relative to form origin.
21. A method as claimed in claim 18 wherein the readily detectable
relationship between the plurality of image plane coordination
marks comprises a readily detectable shape relationship between
individual of the plurality of image plane coordination marks.
22. A method as claimed in claim 21 wherein the readily detectable
shape relationship between the plurality of image plane
coordination marks comprises an identical shape on each of the
plurality of image plane coordination marks.
23. A method as claimed in claim 22 wherein the step of
differentiating the composite image group mark of one form from the
composite image group mark of at least one other form further
comprises the step of employing different shapes to differentiate
composite image group marks on one form with composite image groups
marks on at least one other form.
24. A method as claimed in claim 22 further comprising the step of
differentiating the plurality of composite image group marks on a
first form with the plurality of composite image group marks on
each of two forms printed immediately subsequent to the first
form.
25. A method as claimed in claim 18 for detecting that all image
planes of a print job are in proper sequence, the method further
comprising the steps of: printing a sequence number on a single
image plane of an image; assuring synchronicity of each form;
detecting the sequence number; and assuring that each detected
sequence number is sequential.
26. A method as claimed in claim 18 for detecting that all image
planes of a print job are in proper sequence, the method further
comprising the steps of: assigning a lookup number to at least one
form of a document; printing the assigned lookup number on a single
image plane of an image; assuring synchronicity of each form;
detecting the lookup number; and assuring that each detected lookup
number is in proper sequence.
27. A method for detecting synchronization of printed forms
comprising: printing a plurality of forms, each of the plurality of
forms including a composite image that varies from form to form,
the composite image including a plurality of image planes, each
image plane including printed data and an image plane coordination
mark, the plurality of the image plane coordination marks forming a
composite image group mark, each of the plurality of forms
including an origin, the origin being a reference point on each
form to which each composite image group mark is related, each
composite image group mark of each form being offset by a different
distance from the origin on the form; detecting each of the
composite image group marks and identifying placement of the
composite image group mark with respect to the origin for each of
the plurality of forms; detecting movement of one of the plurality
of image planes from one composite image on one of the plurality of
forms to another composite image on another of the plurality of
forms by identifying a misplacement of one of the image plane
coordination marks from one of the composite image group marks
associated with the one of the plurality of forms; and returning a
synchronization error after the misplacement is identified.
28. A method as claimed in claim 27, wherein identifying the
misplacement of one of the image plane coordination marks from one
of the composite image group marks associated with the one of the
plurality of forms includes detecting the absence of the image
plane coordination mark from the composite image group mark on the
one of the plurality of forms.
29. A method as claimed in claim 27, wherein identifying the
misplacement of one of the image plane coordination marks from one
of the composite image group marks associated with the one of the
plurality of forms includes detecting the presence of an image
plane coordination mark from the composite image group mark from
another form on the one of the plurality of forms.
Description
TECHNICAL FIELD
The present invention relates to digital printing systems and, more
particularly, to a technique for detecting that all components that
make up a completed portion of a form are synchronized.
BACKGROUND ART
In a digital printing system a document may be made up of multiple
forms, each form may be made up of multiple images, and each image
may be made up of multiple image planes. Although these terms are
commonly used in the printing industry, the meaning of these terms
is not precise and tends to vary. As used herein, a form refers to
the contents of a physical portion of a printed media such as a
page. A form may have one or two sides. A form origin is a position
at the top of the form, while a cue mark is a physical mark or a
logical position for pin-feed cueing, identifying the form origin.
A document can be defined as a series of forms that are logically
associated, such as a book or a multi-page billing statement. A
print job can be defined as a series of documents. In some cases, a
document may consist of multiple forms where the forms are printed
2-up across a web of paper. The information printed on one side of
a form is an image, while an image plane is a "layer" of an image
printed by a single print engine. For example, in a processed color
job, each of the CYMK colors is printed by a single print engine in
a separate image plane. A print engine is a marking device such as
a printhead that prints one image plane, or a portion of one image
plane. In an Advanced Function Printing/Intelligent Printing Data
Stream (AFP/IPDS) environment, each of the Object Content
Architecture (OCA) colors is in a separate image plane. An Image
Plane Coordination (IPC) Mark refers to a mark associated with the
image plane. A Composite Image Group (CIG) Mark is a set of IPC
marks consisting of one IPC mark for each image plane in a
form.
In some systems, the form width may be larger than the print engine
print area and multiple print engines may be stitched together side
by side to construct a complete form. A very simple document can be
described as consisting of multiple sequential forms, each with a
single image plane, printed on only one side of the form. Since
such a document is generally printed using a single print engine,
synchronization is not an issue in that case. However, many
documents are more complicated and require multiple print engines
to create each form. Common examples of this are two sided
(duplexed forms), forms printed in multiple colors, or forms made
up of multiple stitched print engines. It is possible for the print
engines to get out of synchronization with each other, or for the
data sent to any of the print engines to get out of
synchronization, such that images or portions of images are no
longer properly synchronized to the proper form. The consequence of
incorrect synchronization is generally very significant and
measures used to detect the condition are necessary.
Various methods exist for detecting and addressing synchronization.
For example, some printing systems print bar codes or other marks
containing data on each side of a form, and after the form has been
printed, read the codes or marks to insure they are properly
synchronized. Existing methods for detecting synchronization
require the printing of specialized marks, a reader or a scanner to
read the marks, and software to interpret the marks and validate
the results. While this system may be suitable for monochrome
applications, it becomes very cumbersome for applications where a
large number of print engines may be used. i.e. 2-up duplex, four
color print job.
It is seen then that there exists a need for an improved means for
detecting synchronization, particularly for printing of multi-color
applications.
SUMMARY OF THE INVENTION
This need is met by the synchronization system and method according
to the present invention, wherein proper synchronization of
information of a portion of a media is detectable. The present
invention detects if all of the image planes that make up an image
are properly coordinated and printed on the same form. The present
invention further detects any errors in synchronization of images
on both the front and the back side of a form. The present
invention further detects any errors in synchronization of images
where the image planes of an image are printed using stitched print
engines.
In accordance with one aspect of the present invention, a method is
provided for detecting that for a print job, all of the components
that make up a completed portion of each form are printed in
synchronicity or in the case of insynchronicity, an error condition
is asserted. The print job comprises at least one form, and each
form may contain more than one image, each image may contains one
or more image planes and the images on each form of a document may
vary.
According to the present invention, each image contains a Composite
Image Group (CIG) mark comprising the set of Image Plane
Coordination (IPC) marks associated with each individual image
plane. An IPC mark is printed by each print engine such that it is
possible via inspection of these marks to determine if the complete
set of image planes that make up a specific image are present. The
IPC marks for each image plane are located within the image such
that such that they do not overlap, and they are positioned
relative to each other in a fixed and known manner such that their
relative positions can be later detected by sensors. The relative
positions for the IPC marks are referenced to the origin of the CIG
mark. Detection of the proper relationship of a set of IPC marks
defines a valid CIG mark and hence, a completed image. In order to
determine the synchronicity of the image, however, the present
invention provides additional information that needs to be
generated and detected.
The set of images that make up a specific form has the origin of
the CIG mark for each image located the same distance from the form
origin. For sequential forms, the distance of the CIG mark from the
form origin varies. After all of the images on a specific form have
been printed, the CIG mark(s) associated with that form, is read
with sensors that determine if all of the IPC marks are valid and
offset the same distance from the form origin. If the distance from
the form origin for all of the IPC marks on a form are the same,
the CIG mark(s) is valid, and a condition is created indicating a
Valid Form. The lack of a Valid Form condition is used by the
printing system to indicate that the information on the form is not
properly coordinated.
Accordingly, it is an object of the present invention to provide a
means for detecting errors in synchronization of all image planes
of all images of all forms in a print job. Other objects and
advantages of the invention will be apparent from the following
description, the accompanying drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a series of successive forms, each comprised of images
with multiple image planes;
FIG. 2 illustrates an error condition where a successive image, as
shown in FIG. 1, has been displaced from its proper location;
FIG. 3 illustrates a form implementing the synchronization
detection technique of the present invention, by incorporating
coordination marks thereon;
FIGS. 4a and 4b show multiple forms illustrating the
synchronization detection technique of the present invention;
and
FIG. 5 illustrates coordination marks printed successively and
being read by sensors during printing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention detects if all of the information printed on
a form, is properly synchronized. The synchronization is detectable
on both the front and back sides of the media. Although the
synchronization detection proposed by the present invention is
particularly suitable for 1-up or 2-up documents, simplex or
duplex, it may be extended to any layout of information.
Furthermore, although the description of the invention refers to a
digital ink jet printing system containing more than one print
engine, it should be obvious to anyone who understands digital
printers that the problem described and the method for detecting
the problem is just as applicable to any digital printing system
with more than one print engine.
Referring now to FIG. 1, there is illustrated a series of
successive forms 10a, 10b and 10c. Each exemplary form is comprised
of one image each with four image planes, 12a, 12b, 12c, 12d, 14a,
14b, 14c, 14d, 16a, 16b, 16c, 16d, 18a, 18b, 18c, 18d. By way of
example, these image planes might correspond to cyan, magenta,
yellow, and black portions of the image. An alternative example is
a system where one print engine prints the left side of the form, a
second print engine prints the right side of the form, and two more
print engines are used to print the back side of the form. When
printing, it is necessary for the multiple image planes to be
properly synchronized so that the resultant composite images
consist of the intended image planes. If one or more of the print
engines get out of synchronization with the others, or if the data
sent to the print engines gets out of synchronization, images, or
portions of images in the case of stitched print engines, are no
longer properly synchronized. The consequence of incorrect
synchronization is generally very significant in that the resultant
form will contain incorrect data.
By way of example, FIG. 2 shows such a condition where the third
image plane represented by 16a, 16b, and 16c has "slipped". Hence,
form 10a is missing an image plane 16a, and forms 10b and 10c each
have the third image plane 16a and 16b, respectively, from the
previous form on them. This results in an error condition where the
images on each form are now made up of improper image planes. In
conventional printing, where each document is the same as the
preceding one, such a slippage is of little consequence. However,
when variable data is printed, such a slippage can be quite
significant. For example, if the documents being printed were
financial statements such a slippage might result in one of the
image planes, containing part of the financial records being print
on a subsequent document that would be mailed to another
individual. While this slippage error might be immediately detected
by the person receiving the printed statement, it might be very
difficult for the operator of the printing system to detect.
Furthermore, such a slippage would typically not involve a single
document, but rather a large print job.
Referring now to FIG. 3, the present invention proposes placing
coordination marks on each form 20, such that it is possible to
tell if all of the components that make up that form are properly
coordinated in relationship to each other. In accordance with the
present invention, each image plane of each image of a form 20
contains an Image Plane Coordination (IPC) Mark 24, printed by the
same print engine used to print that image plane. In FIG. 3, the
image plane coordination marks are shown as rectangles filled with
a different pattern for each image plane. This is so they can be
distinguished from each other in this document. In actual practice,
as will be understood by those skilled in the art, the image plane
coordination marks can be any shape, and can be completely or
partially filled in, so long as they can be recognized as present
or as not present. In a preferred implementation, the Image Plane
Coordination Marks 24 are solid rectangles and can be approximately
1/4'' square, or smaller. For each image on a form, there is a set
of Image Plane Coordination Marks for all of the image planes that
constitute the image. The resultant set defines a Composite Image
Group (CIG) Mark. The makeup of a CIG mark is such that its marks
are positioned having a known offset or relative placement from one
another. The placement of the IPC marks may be accomplished either
in the data preparation, or added to the data by the Raster Image
Processors (RIPS).
FIGS. 4a and 4b illustrate multiple forms 30a, 30b, 32a, 32b, 34a,
34b, 36a, 36b, each having a CIG mark 26 associated therewith. In
order to insure that images or portions of an image from one form
do not get out of sync and print on another form, as was the
exemplary case in FIG. 2, a differentiation is made between forms.
For example, the position of the CIG mark can vary from form to
form. Such a method requires that the CIG mark for consecutive
images be displaced from the form origin 22 (shown in FIG. 3), or
the cue mark, by different distances. In FIG. 4a, each CIG mark 26
is a different distance d from the top of the form. The distance of
the CIG mark 26 from the top of forms 36a and 36b is zero; while
for forms 34a and 34b, the distance is x; and for forms 32a and
32b, the distance is x+y; and finally for forms 30a and 30b, the
distance is x+y+z, where x, y and z are always greater than zero
and each is also greater than the width of an individual IPC mark.
In FIG. 4a, then, the distance d for the first form is at one
origin, and this distance d varies in a cyclical pattern with the
CIG mark moving further away from origin for consecutive documents
and then resetting to an origin position. In the basic
implementation of FIG. 4a, four fixed positions for the start of
the CIG 26 are chosen and are marked as locations 27. The start of
each CIG mark position is a distance that is at least the size of a
IPC mark further away from the origin than the previous CIG mark.
While the CIG mark is shifted relative to the origin by different
amounts from form to form, the relative placement of the individual
IPC marks that make up the CIG mark always remain the same.
As long as the image planes that make up the form are properly
synchronized, the IPC marks making up the CIG will have the proper
relative placement to the other IPC marks. If however, one of the
image planes were to become improperly synchronized, the relative
placement the IPC mark associated with that image plane to the IPC
marks of the other image planes would be incorrect. By way of
example, we will consider a system where the CIG marks are shifted
through four different positions relative to the origin. The CIG
for form 1 is located at the origin, for form 2 it is shifted to 2
inches from the origin, for form 3 is shifted 4 inches from the
origin, for form 4 the CIG marks is shifted 6 inches from the
origin. This pattern is repeated so that on form 5, the CIG mark is
again at the origin. In FIG. 4a, all the CIG marks are complete,
with all the IPC marks properly placed relative to each other. This
indicates that they are properly synchronized.
FIG. 4b illustrates a case where one of the image planes has gone
out of synchronization. The image planes for the upper row of forms
have remained synchronized, so their CIG marks are complete, with
all the IPC marks properly placed relative to each other. While
Form 1B is correct, in Form 2B, a synchronization error has
occurred. The image plane that corresponds to the third IPC mark
28a in the CIG block failed to print. Instead that image plane was
delayed by one form and was printed as part of Form 3B. Its IPC
mark, that if properly synchronized to the other image planes
should have been printed at location 28a, is now printed at 28b.
Similarly, the image plane corresponding to the third IPC mark of
Form 3B is now printed as part of Form 4B with its IPC mark
therefore not being printed in the proper spatial relationship with
the other IPC marks.
By detecting that the third IPC mark is not properly located
relative to the other IPC marks, one can readily detect that the
corresponding image plane has been improperly shifted. Such
detection might be done visually by the system operator, or by
electronic sensor means that will be described later.
While this example shows that shift of the image plane
corresponding to the third IPC mark can be detected, it will be
obvious to those skilled in the art that shifts of any of the image
planes can be detected. Shifts by more than one form can also be
detected. In this example, the CIG was stepped in uniform amounts
from form to form. However, non-uniform steps can be employed. The
example herein also had the CIG mark cyclically through four
positions, relative to the origin. More generally, however, other
cycle lengths can be used. Still more generally, the CIG mark can
be located at random distances from the origin.
In the example shown above, by noting the shift in the placement of
the third IPC mark with respect to the other IPC marks, one could
determine that the image plane corresponding to the third IPC mark
lagged the other image planes by one form. In general, embodiments
where the CIG marks are shifted in a consistent manner from form to
form allow one to identify not only which image plane is shifted,
but also by how much. With this identified, corrective actions can
be taken to shift the errant image plane back into proper
synchronization. For the error shown in FIG. 4b, it would be
necessary to shift the image plane corresponding to the third IPC
mark forward by one form. The image planes would then be properly
synchronized. In this manner, the present invention provides means
to identify synchronization errors and means to re-synchronize the
image planes.
Detection of the synchronization errors in particular forms also
makes it possible to mark or label those forms, either by means of
a mark printed onto the defective forms or by computer tracking, so
that during subsequent processing of the print job, such as during
insertion into the envelopes, these defective forms can be disposed
of. In one preferred embodiment, at the stage that the defective
forms are culled out, these particular forms are identified, by
means of a form distinguishing bar code printed by one of the image
planes. The defective forms can then be reprinted. The combination
of a bar code identifying each document and the CIG marks to
confirm that all image planes of each document are properly
synchronized, can be used to provide the print customer with
confirmation that their print job has been properly printed in its
entirety.
It is sometimes desirable to determine not only that a form is
properly synchronized with all of its parts, but also that it is in
the proper sequence of images for a document. Conventional means
such as printing sequence numbers or bar codes or other marks that
represent the actual sequencing of a document, such as an account
number or other customer or client identification symbol, are
common. With the present invention, this sequence number needs to
be printed on only one of the image planes. Hence, if upon
examination, the sequence of the single image plane is determined
to be correct, and using the teachings of the present invention,
all of the image planes can be determined to be synchronized, then
all of the image planes will be known to be in the proper
sequence.
Unfortunately, with a cyclically repeating placement of the CIG
marks from form to form is that if an image plane is shifted by an
amount equal to the repeat length of the CIG marks, the error can't
be detected. For our example system described above, if the cyan
image plane where to lead the other image planes by four forms,
form 5 of the cyan image plane would be printed along with the form
1 of the other image planes. As the CIG marks for both of these
forms are located at the origin, one can't detect the synchronizing
error. In an alternative embodiment, the CIG marks are offset by a
random, or a non-repeating distance, such that two consecutive CIG
marks are guaranteed never to be at the same offset distance. In
this way, synchronization errors of any image plane slippage amount
can be detected, at least within a few forms. This embodiment may
be advantageous in a case where a set of forms repeats, and an
error occurs in coordination that matches the repeat.
It should be noted that synchronization errors can be detected
using the present invention if the CIG marks are only printed on
alternately printed forms. For example, if the CIG marks are only
printed on the odd number forms such as forms 1 and 3 of FIG. 4a, a
slippage of one of the image planes by one form will result in
printing an IPC mark on an even number form such as forms 2 and 4
where none were to be printed. Detection of the error can therefore
be made as well. Further, it would be obvious to add the IPC marks
only to selected forms in a document to check the synchronicity of
the forms that make up the document only once per document.
Further, it would be obvious to add IPC marks only to selected
forms between documents to check the synchronicity of the forms
that make up the document only once per document but to not print
the IPC marks on the document itself. For example the IPC marks
could be printed on separator pages between documents.
As illustrated in FIG. 5, a sensor is used to detect that all of
the IPC marks that make up a single CIG mark are present by looking
for completeness of the CIG mark indicators 26. Completeness is
indicated when all of the IPC marks 24 for the image are in the
right relationship to each other at the time of inspection. The CIG
mark indicators 26 may be sensed either be a single sensor 38 or
multiple sensors 38. The sensor or sensors look for the IPC marks
to be present at the known offset relationship to each other. When
the proper spatial relation of the IPC marks is detected, a signal
or condition indicating a complete, synchronized image can be
asserted indicating a good CIG (Composite Image Group) condition.
Due to the common spatial relationships of the components of the
CIG mark from the origin of the form, the inspection of a form does
not need to be done at any specific time or position of the form.
The simple condition of coincidence of all of the IPC marks by
itself indicated a good form.
It is an advantage of the present invention that the
synchronization detection can be applied to both the front and rear
sides of a printed media, by printing the IPC marks 24 on each side
of the media. A condition where the CIG condition exists
simultaneously for both sides of a form indicates a Complete Form
condition. It is a further advantage of this invention that
synchronization of 2-up (or "n" up) documents where multiple forms
are printed across the web can be verified with respect to each
other and checked to insure that all of the image planes for each
form have their CIG marks located in the exact same position across
the web and/or on both sides of the web relative to the origin. For
example, in FIG. 4a, forms 30a and 30b have their CIG marks located
identically to each other; and this is the case for forms 32a and
32b, forms 34a and 34b, and forms 36a and 36b.
In the embodiment of the invention described above, the IPC marks
were located relative to each other according to a predefined,
readily detected spatial relationship. The collection of IPC marks,
that is the CIG mark, for each form was shifted from form to form
relative to the origin to differentiate the marks of one form from
those of other forms. The differentiation of the composite image
group marks on one form from the composite image group marks on at
least one other form, is such that the readily detectable
relationship between image plane coordination marks that make up
each composite image group mark is intact if the image planes are
properly synchronized, but broken if the image planes are not
properly synchronized. The means for differentiating can be applied
such that composite image group marks on a first form can be
differentiated from composite image group marks on each of two or
more forms printed immediately subsequent to or preceding the first
form.
In accordance with the present invention, the IPC marks may
comprise shapes, letters, numbers, or other marks. The IPC marks
for the different image planes have a predetermined, readily
detectable relationship with the other IPC marks of the composite
image. While the preceding embodiment utilized a particular
predefined, readily detectable spatial relationship between the IPC
marks, many other predefined, readily detectable relationships are
possible. One such relationship is that the shapes, letters or
numbers match. The CIG marks are differentiated from form to form
by changing the shape, letter or number being used from form to
form. In this way, the predetermined, readily detected shape
relationship between the IPC marks on a form is intact if the image
planes are properly synchronized, but broken if the image planes
are not properly synchronized.
In one preferred embodiment separate sensors are used for each IPC
mark that make up the CIG mark. The CIG mark sensors are located
adjacent to the paper path downstream of where all of the images of
a form have been printed and all forms across the web have been
printed. In accordance with one embodiment of the present
invention, these sensors are positioned such that the relative
placement of the sensors matches the desired relative placement of
the IPC marks. As a properly synchronized set of forms crosses the
sensors, the matched relative placement of the sensors and the IPC
marks will result in the IPC marks being detecting concurrently by
their corresponding sensors. This condition creates a Forms In
Sync, or FIS, condition. The FIS condition is latched and held
until the next top of a form reaches the sensors. Alternatively,
the CIG marks may be oriented in other positions, so long as the
CIG mark condition can be determined. A set of physical sensors can
be mounted over the paper path with the same offsets as the
individual IPC marks and as the IPC marks pass under the sensors
and are detected, a condition of simultaneous detection can be
made. The simultaneous detection of all of the IPC marks indicates
a good CIG mark and, hence, is an indication that the image is
complete. It will be obvious to those skilled in the art that the
physical relationship of the sensors to each other provides one
method of determining the spatial relationship. However, the
sensors can actually be at any location suitable for sensing the
IPC marks, and the relationship can be interpolated via software or
electronics.
In accordance with the present invention, printing is controlled by
a print controller that manages the print information. As the job
prints, the controller tracks the location of the first form along
the print path. The controller tracks or senses when the top of
each form reaches the CIG mark sensors. The sensors sense the
position of the CIG mark and the FIS signal is reset. If this is
the first form it, discards the FIS value. As the form progresses,
each of the CIG mark sensors look for the document complete signal.
The output from the multiple CIG sensors is ANDed together such
that a Form In Sync condition is generated. When the top of the
next form is reached, the controller expects to see the Form In
Sync condition. If the controller does not see this condition, an
out-of-sync condition exists and the controller can take
appropriate action to notify an operator or halt production of the
job.
In another preferred embodiment, a single sensor is employed. The
detector senses light reflected from the paper. A mask is placed
between the paper and the sensor. The pattern of openings in the
mask is made to coincide with the normal pattern of IPC marks. When
an IPC mark is aligned with one of the opening in the mask, it
reduces the amount of the light detected by the sensor. If IPC
marks are aligned with each of the openings in the mask, which
would indicate that the IPC marks have the proper relative
placement of a properly synchronized form, the light detected by
the sensor is reduced to a minimum level. A threshold detection
circuit applied to the sensor output can then be used to determine
whether the detected light intensity has reached the proper minimum
level indicative of a properly synchronized form.
Having described the invention in detail and by reference to the
preferred embodiment thereof, it will be apparent that other
modifications and variations are possible without departing from
the scope of the invention defined in the appended claims.
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